1. Field of the Invention
The invention relates to a method and device for adjusting and/or controlling the uniformity of a plasma process.
2. Description of Related Art
In semiconductor manufacturing, the complexity of devices formed on semiconductor substrates continues to increase at a rapid pace, while the size of features, such as transistor gates, continues to decrease well below the 93 nanometer (nm) technology node. As a result, manufacturing processes require increasingly sophisticated unit process and process integration schemes, as well as process and hardware control strategies to ensure the uniform fabrication of devices across the substrate. For example, during the fabrication of a gate electrode structure in a transistor device, patterning systems and etching systems, which facilitate the formation of the gate structure in a plurality of material films formed on the substrate, are required to achieve and preserve the gate structure critical dimension (CD) vertically within the device being fabricated as well as laterally across the substrate from device-to-device. A reduction of variations in the CD, as well as variations in profile and side-wall angle (SWA), across the substrate can affect the uniform yield of high performance devices (i.e., speed, power consumption, etc.).
The fabrication of integrated circuits (IC) in the semiconductor industry typically employs plasma to create and assist surface chemistry within a processing chamber necessary to remove material from and deposit material on a substrate. In general, plasma is formed within the processing chamber under vacuum conditions by heating electrons in the presence of an electric field to energies sufficient to sustain ionizing collisions with a supplied process gas. Moreover, the heated electrons can have energy sufficient to sustain dissociative collisions and, therefore, a specific set of gases under predetermined conditions (e.g., chamber pressure, gas flow rate, etc.) are chosen to produce a population of charged species and chemically reactive species suitable to the particular process being performed within the chamber (e.g., etching processes where materials are removed from the substrate or deposition processes where materials are added to the substrate).
In semiconductor manufacturing, numerous techniques exist for creating plasma including, but not limited to, capacitively coupled plasma (CCP) systems, inductively coupled plasma (ICP) systems, electron cyclotron resonance (ECR) plasma systems, helicon wave plasma systems, surface wave plasma systems, slotted plane antenna (SPA) plasma systems, etc. Plasma is formed from the interaction of the supplied process gas with electro-magnetic (EM) field propagation at frequencies in the radio frequency (RF) or microwave spectrum.
However, common to many plasma processing systems, process performance suffers from process non-uniformities, including a spatially non-uniform plasma density. During an etching process, process non-uniformities may lead to spatial non-uniformities in the distribution of a feature critical dimension (CD) across the substrate or a side-wall angle (SWA) across the substrate. For example, during gate structure formation, it is desirable to achieve a uniform distribution of the gate width (at the top and bottom of the etched feature, as well as the region there between) across the substrate following an etching process or series of etching processes. Failure to achieve uniform or substantially uniform process results leads to a reduction in the yield of high performance devices as indicated above.
Therefore, since improving process uniformity in semiconductor manufacturing has always been an important goal, there remains a need for systems that improve process parameter uniformity across the surfaces of substrates during processing.